The interpretation and prediction of the properties of opaque minerals from crystal chemical models

Various approaches to the modelling of the electronic structures of opaque minerals are briefly outlined. It is argued that a simplified approach based chiefly on molecular orbital theory and incorporating some elements of band theory is most useful in the interpretation and prediction of the properties of opaque minerals. Models can be developed using data from spectroscopic (especially X-ray and UV photoelectron and X-ray emission spectra) techniques, from quantum mechanical calculations and on the basis of electrical and magnetic properties. The best "working models" employ data from all of these sources.

The development and application of electronic structure models are considered using the pyrite-tyoe disulfides and the hematite-ilmenite series as examples. Properties such as colour, reflectivity, hardness, stability and thermochemical data, and solid solution behaviour are interpreted using the models. The property of optical anisotropy is discussed with molybdenite as an example. The importance of electronic structure models for understanding mineral behaviour is emphasised with reference to these and other examples of opaque minerals.